In general, a steam generator which constitutes a facility such as a turbine generator for generating electricity with use of steam is provided with a steam-water separator in order to prevent erosion and to prevent energy transmission efficiency. As an example of a steam-water separator, there is one which has a cylinder-shaped riser provided in the gravitational direction and in which a gas-liquid two-phase flow composed of a mixture of steam and hot water rises, a downcomer barrel arranged so as to surround the periphery of this riser, and a swirl vane provided within the riser.
With this type of configuration, a gas-liquid two-phase flow introduced from the bottom end part of the riser is swirled by the swirl vane while rising, and is separated into steam and hot water. While the steam continues to swirl and rise towards the upper side of the riser, the hot water descends within the downcomer space defined by the riser and the downcomer barrel.
Here, there is a limit in separating a gas-liquid two-phase flow into steam and water by making it swirl, and so-called carry-under occurs, in which hot water descending inside the downcomer space entrains steam. Moreover, carry-over occurs, in which steam rising towards the upper side of the riser entrains hot water. Therefore, various techniques have been disclosed in order to reduce the level of carry-under and carry-over.
For example, there is one in which a plurality of blades provided projecting from a swirl vane are arranged so as to overlap with each other in the axial direction, and a deck plate is provided above the riser. Further, between the deck plate and the downcomer barrel 4, there is formed a slit-shaped opening part, and at the exit of the downcomer space, an intermediate deck plate with an outer diameter substantially the same as that of the downcomer barrel, is installed on the riser (for example, refer to Patent Document 1).
According to this, it is possible to make it unlikely for the separated water to exit from between the respective blades of the swirl vane. Moreover, it aims to reduce carry-over by causing rising steam to collide with the deck plate, and reduce carry-under by causing hot water to collide with the intermediate deck plate.